CF4 / O2 식각 가스계를 사용한 텅스텐 박막의 건식 식각 연구

Abstract

Dry etching of LPCVD tungsten film was performed using CF₄/O₂ plasma in both reactive ion etching(RIE) and plasma etching(PE) modes. The etch rate of tungsten and the selectivity of tungsten to SiO₂ were examined as a function of oxygen content in feed gas, pressure and RF power. The maximum etch rate in PE and RIE modes were observed at 40 and 50% O₂ in feed gas, respectively. The maximum selectivities of tungsten to SiO₂ in both modes were about 16 and 2.3, respectively. Mass spectroscopy(MS) and optical emission spectroscopy(OES) were used to identify the reactive species in CF₄/O₂ plasma. The results of MS and OES analyses in measuring the etch rate as a function of O₂ percent suggest that WOF₄ and WF_6 are main etch products for tungsten etching. The maximum etch rate was obtained at 0.6 torr for PE mode and 200 mtorr for RIE mode. With the increase of RF power, the etch rates of both tungsten and SiO₂ increased, but the selectivity of tungsten to SiO₂ decreased.